大学四级-25及答案解析.doc

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1、大学四级-25 及答案解析(总分：693.00，做题时间：90 分钟)一、BPart Writing(总题数：1，分数：106.00)1.越来越多的人涌入大城市，有些问题随之产生； 2比较明显的问题有； 3我对这种现象的想法。BCity Problems/B（分数：106.00）_二、BPart Reading (总题数：1，分数：70.00)BTo Save Trees, Fighting One Alien Insect with Others/BRusty Rhea sighs wistfully as he talks about the beauty and peace of sta

2、nding amid a grove (小树林) of deep green hemlocks in Appalachia, some of them up to 160 feet ( 50 meters ) tall and more than 500 years old.“This is a very special tree,“ said Rhea, an entomologist for the U.S. Forest Services Forest Health Protection program in Asheville, North Carolina. “I was broug

3、ht up here, and I dont want to see another species go by the wayside.“The evergreen trees, a hallmark of southern Appalachias national parks, are Under attack by an invasive insect barely visible to the eye but potent enough to fell the giants of the eastern United States old-growth forests.Already

4、the tiny bug from Japan, known as the hemlock woolly adelgid (HWA), has killed upward of 95 percent of the hemlocks in Virginias Shenandoah National Park. Now they are making their way through the half-million-plus-acre (200,000-plus-hectare) Great Smoky Mountains National Park in North Carolina and

5、 Tennessee.The hemlocks shade streams, keeping water temperatures just right for brook trout (鲑鱼) and other fish. They also house birds such as the black-throated green warbler, solitary vireo, and northern goshawk, all three of which mainly shelter in stands of hemlock trees.Because of the insects

6、broad impact on the entire ecosystem of southern Appalachia, HWA stands to cause wider damage than the American chestnut blight (枯萎病) of the early 1900s. That fungus from Europe killed off the once dominant chestnut trees from the northeast United States to the southern Appalachian Mountains.In addi

7、tion, a species related to HWA, the balsam woolly adelgid, has already killed about 90 percent of the mature Fraser fir trees in the Smokies.BActing Quickly/BHWA arrived in the U.S. Pacific Northwest via nursery plants from Japan in 1924. By 1951 the tiny invader had been found in Virginia. Since th

8、en the insect has spread to more than 15 U.S. states.The key to killing the HWA is to catch if early and act quickly. Its already well established in the Great Smoky Mountains, where Rhea and others are trying to stem the spread of the bugs.HWA multiply quickly: All of the insects are females that r

9、eproduce asexually (无性地), laying several hundred eggs a year. When they get to the nymph, or crawler, stage, they are dormant from about June until October, after which they emerge and establish themselves on trees.Winds and birds and other animals spread the crawlers through the forest.HWA crawlers

10、 feed on the new growth of hemlocks by piercing the twigs that hold the branches, sucking the sap, and injecting toxic saliva. The needles turn from a deep green to a grayish green and eventually die, depriving the tree of nutrition from photosynthesis.An infected tree usually dies within five years

11、 of initial attack: Infection is signaled by either a white, cottonlike material that appears along a trees twigs or by the “baldness“ of a trees upper branches.BPlans of Attack/BIn the Pacific Northwest the hemlocks seem to be tolerant of the creatures feeding, and in the cold northeast, winters se

12、em to keep them at bay. But in the warm southeast, with weather approximating that of the insects native Asian homes, they thrive.Chemical sprays-such as insecticidal soaps and horticultural oils as well as trunk or soil injections-have helped to kill some of the HWA infestations.But spraying must b

13、e repeated every six months, and injections are expensive and last only two years at most. These methods cant be used conveniently or safely in remote areas or near the streams where hemlocks grow thickly.Long term, the best way to control the pests appears to be releasing other insects that feed ex

14、clusively on HWA. Scientists have studied HWA in Japan and China and identified three such species. One of them, the Sasajiscymnus tsugae (St) beetle, was released in areas of Great Smoky Mountains National Park in 2002.Studying what controls a species in its native habitat-including climate, predat

15、ors, and host resistance-provided clues about which insects to use against HWA, said Kristine Johnson. Based in Gatlinburg, Tennessee, Johnson is a supervisory forester for Great Smoky Mountains National Park.“Biological control is the only long-term hope to save the trees in the backcountry (穷乡僻壤),

16、“ she said. “We have 800 square miles (2,100 square kilometers) of contiguous wilderness. We value the native forest, and its entirely worth defending.“BRisky Business/BReleasing one species of non-native bug to kill another could be risky business, potentially creating another type of infestation.

17、But scientists first quarantined and studied the HWA-killer insects.They believe the St beetles are the best answer tn the HWA problem and that they wont cause side damage. This tiny black female beetle, the size of a poppy seed, is already spreading in the Great Smoky Mountains.But the beetle and o

18、ther HWA-killer insects are seasonal, so it will take several different ones operating year-round to keep HWA in check, Rhea said. He doesnt believe HWA will be completely eradicated (根除) but will instead be kept in balance by the predator insects. “Were trying to insert a balance in a system thats

19、out of balance,“ he said.Each St beetle can lay 200 to 300 eggs, said Ernest Bernard, professor of entomology and plant pathology at the University of Tennessee in Knoxville.Bernards laboratory is one of several that are breeding the beetles.“Each beetle eats hundreds of baby adelgids a year,“ he sa

20、id. And about 120,000 of the beetles have been released in the past couple years in the Smokies, but it is still too early to measure their impact.One good sign, Bernard said, is hat some beetle larvae (幼虫) have been found in areas where they were not released, indicating that the HWA killers may be

21、 reproducing and spreading.（分数：70.00）(1).The passage gives a general description of an invasive insect, HWA.（分数：7.00）填空项 1:_(2).Hemlock is a hallmark of southern Appalachias national parks.（分数：7.00）填空项 1:_(3).The invasive insect, known as the hemlock woolly adelgid (HWA), is from Japan.（分数：7.00）填空项

22、1:_(4).The key to killing the HWA is to catch it early and act quickly.（分数：7.00）填空项 1:_(5).An infected tree usually dies immediately.（分数：7.00）填空项 1:_(6).The Hemlock in the U.S. will be saved from HWA soon.（分数：7.00）填空项 1:_(7).The long term, best way to control the pests HWA is spraying.（分数：7.00）填空项 1

23、:_(8).Since 1951 the HWA has spread to more than _ .（分数：7.00）填空项 1:_(9).Releasing one species of non-native bug to kill another could create _ .（分数：7.00）填空项 1:_(10).It will take several different insects operating year-round to _ .（分数：7.00）填空项 1:_三、BPart Listenin(总题数：3，分数：105.00)BQuestions 11 to 18

24、are based on the conversation you have just heard./B（分数：56.00）A.1016.B.1060.C.508.D.580.A.Father and daughter.B.Uncle and niece.C.Aunt and nephew.D.Cousins.A.She wasnt invited.B.She wasnt ready to come.C.She altered her decision.D.She forgot the invitation.A.The door needs repairing.B.He had lost al

25、l his keys.C.He couldnt open the door.D.He wanted the woman to help him.A.Shes rather happy to hear so.B.Shes disappointed to hear so.C.Shes unhappy to hear so.D.Shes surprised to hear so.A.He thought it was a good car.B.He thought it was too noisy.C.He thought there was something wrong with the car

26、.D.He didnt like it.A.In a car.B.In a train.C.In a ship.D.In a plane.A.Shell go to the concert.B.Shell have a meeting.C.Shell watch her neighbors children.D.Shell visit her neighbor.BQuestions 19 to 22 are based on the conversation you have just heard./B（分数：28.00）A.The early history of bookbinding.B

27、.How old books become valuable.C.Economical ways to protect old books.D.Why some books decay.A.They are often handled improperly by readers.B.The paper is destroyed by chemicals.C.The ink used in printing damages the paper.D.The glue used in the binding loses its strength.A.They are difficult to rea

28、d.B.They are slowly falling apart.C.They were not made from wood pulp.D.They should be stored in a cold place.A.Get some books for the man to look at.B.Ask the man to look over her notes.C.Continue her research in the library.D.Find more information on how books are preserved.BQuestions 23 to 25 are

29、 based on the conversation you have just heard./B（分数：21.00）A.Which major the woman will be choosing.B.An anthropology course the woman is taking.C.How to find a job in publishing.D.Which anthropology professors the man recommends.A.It is not as difficult as she had thought it would be.B.She would li

30、ke her professor to explain it more clearly,C.She took a class on it last semester.D.Her professor will write a book on it soon.A.Her professor.B.A classmate.C.Her former boss.D.A foreign diplomat.四、BSection B/B(总题数：3，分数：70.00)BPassage OneQuestions 26 to 28 are based on the passage you have just hea

31、rd./B（分数：21.00）A.Because nobody knew his address.B.Because nobody knew his age.C.Because Penurys private life was a secret.D.Because Penury was still a bachelor at the age of forty-five.A.He did not spend money freely.B.He was always well-dressed.C.He had a luxurious car.D.He worked hard for a livin

32、g.A.A photographer.B.A burglar.C.A reporter.D.A professor.BPassage TwoQuestions 29 to 32 are based on the passage you have just heard./B（分数：28.00）A.In 1809.B.In 1863.C.In 1865.D.In 1860.A.Four years.B.Five years.C.Three years.D.Six years.A.A soldier.B.A thief.C.A government officer.D.An actor.A.Beca

33、use they didnt like Lincoln being their President.B.Because they wanted to set up their own government.C.Because they disagreed with Lincoln on the abolishment of slavery.D.Because they wanted to stage a war against Lincolns government.BPassage ThreeQuestions 33 to 35 are based on the passage you ha

34、ve just heard./B（分数：21.00）A.10 points.B.2 points.C.15 points.D.5 points.A.They will take one of the six major tests.B.They will have to write a composition.C.They will be given a pop test.D.They will be required to read a short story in class.A.An essay.B.A magazine article.C.A poem.D.A short story.

35、五、BSection C/B(总题数：1，分数：77.00)Scientists have developed a new cancer drug. So far, they have tested it only onU (36) /Uanimals. The drug is designed toU (37) /Uand kill cancer cells but not healthy cells.First, the drug enters the cancer and destroys the supply of blood. Then it releasesU (38) /Uto

36、destroy the cancer ceils.Researchers at the Massachusetts Institute of Technology in Cambridge carried out the study. TheU (39) /Uappeared in NatureU (40) /U. A school news release called the drug an “anti-cancer smart bomb.“Ram Sasisekharan is a professor at M.I.T. He says his team had toU (41) /Ut

37、hree problems. They had to find a way to destroy the blood vessels, then toU (42) /Uthe growth of new ones. But they also needed the blood vessels to supply chemicals to destroy the cancer.So, the researchers designed a two-part “nanocell“. The cell isU (43) /Uin nanometers, or one thousand milliont

38、h of a meter.U (44) /U.The scientists say it was small enough to pass through the blood vessels of the cancer, but it was too big to enter normal blood vessels. The surface of the nanocells also helped them to avoid natural defenses.U (45) /U. That cut off the blood supply and trapped the nanocell i

39、nside the cancer. Then, the nanocell slowly released chemotherapy drugs to kill the cancer cells.U (46) /U.（分数：77.00）(1).（分数：7.00）填空项 1:_填空项 1:_填空项 1:_填空项 1:_填空项 1:_填空项 1:_填空项 1:_填空项 1:_填空项 1:_填空项 1:_填空项 1:_六、BPart Reading (总题数：1，分数：90.00)Many of the most damaging and life threatening types of weath

40、er-torrential rains, severe thunderstorms, and tornadoes-begin quickly, strike suddenly, and disappear rapidly, destroying small regions while leaving neighboring areas untouched. Such event as a tornado struck the northeastern section of Edmonton, Alberta, in July 1987. Total damages from the torna

41、do exceeded 250 million, the highest ever for any Canadian storm.Conventional computer models of the atmosphere have limited value in predicting short lived local storms like the Edmonton tornado, because the available weather data are generally not detailed enough to allow computers to study carefu

42、lly the subtle atmospheric changes that come before these storms. In most nations, for example, weather-balloon observations are taken just once every twelve hours at locations typically separated by hundreds of miles. With such limited data, conventional forecasting models do a much better job pred

43、icting general weather conditions over large regions than they do forecasting specific local events.Until recently, the observation intensive approach needed for accurate, very short-range forecasts, or “Nowcasts“, was not feasible. The cost of equipping and operating many thousands of conventional

44、weather stations was extremely high, and the difficulties involved in rapidly collecting and processing the raw weather data from such a network were hard to overcome. Fortunately, scientific and technological advances have overcome most of these problems. Radar systems, automated weather instrument

45、s, and satellites are all capable of making detailed, nearly continuous observation over large regions at a relatively low cost. Communications satellites can transmit data around the world cheaply and instantaneously, and modem computers can quickly compile and analyze this large volume of weather

46、reformation. Meteorologists (气象学者) and computer scientists now work together to design computer programs and video equipment capable of transforming raw weather data into words, symbols, and vivid graphic displays that forecasters can interpret easily and quickly. As meteorologists have begun using

47、these new technologies in weather forecasting offices, Nowcasting is becoming a reality.（分数：90.00）(1).It can be inferred from the passage that the value of damages from torrential rains, severe thunderstorms and tornadoes is _ .（分数：18.00）填空项 1:_(2).Why do conventional models of the atmosphere fail to predict such a short-lived tornado?（分数：18.00）填空项 1:_(3).It can be inferred from the passage that conventional forecasting models are n